Complementary goods tend to...

Complementary goods are products that are typically used together, meaning that the demand for one good is closely linked to the demand for another. When the use of one good increases, it often leads to an increase in the use of the complementary good as well. For instance, if the price of coffee decreases and more people buy coffee, they might also buy more sugar and cream, which are complementary goods to coffee. Consequently, an increase in demand for coffee results in an increase in demand for its complements due to their interrelated uses.

The fundamental principle behind complementary goods is that their utility is often maximized when they are consumed together. When consumers expect to get more enjoyment or utility from using two goods together, they tend to buy more of both as a direct result of the relationship they have with one another. This interdependence is what leads to the correct answer regarding the increase in demand when complementary goods are used together.